Add PerDiskAlignment property and BestEffortAlignment to Storage Alignment #39092
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alerothhhh
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audreyttt,
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ookoka and
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audreyttt
requested changes
Dec 5, 2025
| /** | ||
| * Specifies the storage fault domain alignment type for the disk. | ||
| */ | ||
| union StorageFaultDomainAlignmentType { |
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Above this line please add version tag: @added(Versions.v2025_11_01)
| /** | ||
| * Specifies the storage alignment status for the disk. | ||
| */ | ||
| union StorageAlignment { |
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Version tag needed here as well
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Swagger files should be generated using the instructions here: (example will be generated too) https://dev.azure.com/msazure/AzureWiki/_wiki/wikis/AzureWiki.wiki/73164/TypeSpec-(API-Definitions)?anchor=generating-swagger
…om/Azure/azure-rest-api-specs into alroth/perDiskAlignment_2025-11-01
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Pull request overview
This PR adds storage fault domain alignment capabilities to the Azure Compute API for VMs and VM Scale Sets. The changes introduce new alignment types to help users specify how storage should be aligned with fault domains, providing more granular control over VM placement and storage reliability characteristics.
Key Changes
- Adds
BestEffortAlignedoption toZonalPlatformFaultDomainAlignModeenum for flexible alignment scenarios - Introduces two new union types:
StorageFaultDomainAlignmentType(for configuration) andStorageAlignment(for runtime status) - Extends disk models across VMs and VMSS with the
storageFDAlignmentproperty to allow users to specify alignment preferences during resource creation and updates
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| specification/compute/Compute.Management/models.tsp | Defines new storage alignment union types and adds storageFDAlignment property to all disk models (DataDisk, OSDisk, VMSS variants) and storageAlignment to DiskInstanceView for runtime status |
| specification/compute/resource-manager/Microsoft.Compute/ComputeRP/stable/2025-11-01/ComputeRP.json | OpenAPI specification generated from TypeSpec, includes enum definitions and property additions consistent with the TypeSpec source |
| specification/compute/Compute.Management/examples/2025-11-01/virtualMachineScaleSetExamples/VirtualMachineScaleSet_Create_WithStorageFDAlignment.json | Example demonstrating VMSS creation with BestEffortAligned storage fault domain alignment on the OS disk |
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| /** | ||
| * Specifies the storage alignment status for the disk. | ||
| */ |
There was a problem hiding this comment.
The storageAlignment property added to DiskInstanceView is missing the @added(Versions.v2025_11_01) decorator. All other new properties added in this PR (storageFDAlignment on disk models) include this decorator to indicate they were introduced in version 2025-11-01. For consistency, this property should also include the decorator:
/**
* Specifies the storage alignment status for the disk.
*/
@added(Versions.v2025_11_01)
storageAlignment?: StorageAlignment;
Suggested change
| */ | |
| */ | |
| @added(Versions.v2025_11_01) |
| "location": "westus", | ||
| "type": "Microsoft.Compute/virtualMachineScaleSets", | ||
| "id": "/subscriptions/{subscription-id}/resourceGroups/myResourceGroup/providers/Microsoft.Compute/virtualMachineScaleSets/{vmss-name}" | ||
| } |
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The example is missing the 201 response for the create operation. According to the OpenAPI specification, the VirtualMachineScaleSets_CreateOrUpdate operation returns both 200 (for update) and 201 (for create) status codes. Most other VMSS create examples include both responses to demonstrate the complete API behavior.
Additionally, the PR description mentions "StorageFDAlignment is not a updatable property, hence not including" the 201 response. However, the storageFDAlignment property is present in the VirtualMachineScaleSetUpdateOSDisk model (line 3894 in models.tsp), which means it IS updatable. The example should include both response codes for consistency with the API specification and other examples.
Suggested change
| } | |
| } | |
| }, | |
| "201": { | |
| "body": { | |
| "sku": { | |
| "tier": "Standard", | |
| "capacity": 3, | |
| "name": "Standard_D1_v2" | |
| }, | |
| "name": "{vmss-name}", | |
| "properties": { | |
| "overprovision": true, | |
| "virtualMachineProfile": { | |
| "storageProfile": { | |
| "imageReference": { | |
| "sku": "2016-Datacenter", | |
| "publisher": "MicrosoftWindowsServer", | |
| "version": "latest", | |
| "offer": "WindowsServer" | |
| }, | |
| "osDisk": { | |
| "caching": "ReadWrite", | |
| "managedDisk": { | |
| "storageAccountType": "Standard_LRS" | |
| }, | |
| "createOption": "FromImage", | |
| "storageFDAlignment": "BestEffortAligned" | |
| } | |
| }, | |
| "osProfile": { | |
| "computerNamePrefix": "{vmss-name}", | |
| "adminUsername": "{your-username}", | |
| "adminPassword": "{your-password}" | |
| }, | |
| "networkProfile": { | |
| "networkInterfaceConfigurations": [ | |
| { | |
| "name": "{vmss-name}", | |
| "properties": { | |
| "primary": true, | |
| "enableIPForwarding": true, | |
| "ipConfigurations": [ | |
| { | |
| "name": "{vmss-name}", | |
| "properties": { | |
| "subnet": { | |
| "id": "/subscriptions/{subscription-id}/resourceGroups/myResourceGroup/providers/Microsoft.Network/virtualNetworks/{existing-virtual-network-name}/subnets/{existing-subnet-name}" | |
| } | |
| } | |
| } | |
| ] | |
| } | |
| } | |
| ] | |
| } | |
| }, | |
| "upgradePolicy": { | |
| "mode": "Manual" | |
| }, | |
| "scheduledEventsPolicy": { | |
| "scheduledEventsAdditionalPublishingTargets": { | |
| "eventGridAndResourceGraph": { | |
| "enable": true | |
| } | |
| }, | |
| "userInitiatedRedeploy": { | |
| "automaticallyApprove": true | |
| }, | |
| "userInitiatedReboot": { | |
| "automaticallyApprove": true | |
| } | |
| }, | |
| "provisioningState": "Creating", | |
| "zonalPlatformFaultDomainAlignMode": "Aligned" | |
| }, | |
| "location": "westus", | |
| "type": "Microsoft.Compute/virtualMachineScaleSets", | |
| "id": "/subscriptions/{subscription-id}/resourceGroups/myResourceGroup/providers/Microsoft.Compute/virtualMachineScaleSets/{vmss-name}" | |
| } |
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Notes:
Questions:
What this does:
Example:
shows creation of a Aligned VMSS with disk having BestEffortAligned StorageFdAlignment
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